So, you’ve decided to install a concrete sleeper retaining wall, but are your DIY hands up to the task?

With a few simple steps and the right supplies, you can build a concrete sleeper retaining wall that will stand the test of time, but there are some important factors that need to be taken into consideration, like if your wall goes over a certain height and building permit, you may be required to consult a structural engineer and contact your Local Council for approval.

Regulations and Engineering

Engineering is a cost to factor in depending on your wall height. See below the Australian Standards 

• AS4678-2002 – Earth Retaining Structures sets the overall standards for retaining walls in Australia.

Other Australian Standards that may be relevant include:

• AS/NZ1170.0-2002 Structural design actions – General principles
• AS/NZ1170.0-2011 Structural design actions – Wind actions
• AS3600-2009 Concrete structures
• AS/NZ2312-2002 Guide to the protection of structural steel against atmospheric corrosion by the use of protective coatings.

On top of these Australian Standards, councils have their own regulations, so it is best to do your research to ensure there are no hiccups along the way. 

Council Requirements

When planning to build a retaining wall it is always recommended to contact your local council for any information or planning approvals.

• Brisbane City Council Building a retaining wall
• Ipswich City Council Building and development compliance
• Gold Coast Council – Retaining walls
• Toowoomba – Building approvals and heights for retaining walls
• Moreton Bay Regional Council – Building approval
• Logan City Council – Building Approvals Fact Sheet
• Redlands City Council – Minor building projects
• Sunshine Coast Council – Property fences and retaining walls

Foundations

Foundations are possibly the most important part of a retaining wall considering it is going to be holding a dense amount of earth. The required foundations will vary depending on soil properties, wall height and engineering requirements/ council regulations. By ensuring the foundations are accurate and to specification it ensures avoiding issues later down the track.

Drainage

Another important factor to consider as incorrect or inadequate drainage will eventually compromise the wall and cause the wall to fail. We recommend using agi pipe and geotextile fabric for concrete sleepers and you can purchase these from us at Australian Landscape Supplies online or from our Eagle Farm Warehouse.  

Materials

Timber, besser blocks, concrete sleepers and rock, there are plenty of options so make sure you do your research. Timber can be the cheapest option but never lasts as long as alternate options; bricks and besser blocks are strong and durable but are labour intensive; concrete sleepers on the other hand are ideal because not only are they aesthetically pleasing to the eye, but they are strong, durable and require minimal maintenance.

Planning

The part that lets a lot of DIYers down, you need to ensure you have a full plan when it comes to building any retaining wall from start to finish. Consider curves, obstructions, access issues for machinery and trucks and consult with an engineer and your local council if required. Ensure your timeframe allows you to have your materials delivered at least a day before concrete is organised. Ultimately, allow yourself time between the different stages that way everything should still run smoothly regardless of any hiccups that may arise.

How to Install Concrete Sleepers

Building a retaining wall from concrete sleepers isn’t overly complex, but it does require some finesse and knowledge. 

First things first, you need to identify where your cement sleepers will go. Clear any topsoil and vegetation from the area you plan to build. 

Level the site and make sure to leave a 300mm gap behind the wall for your aggregate and drainage pipe. 

 2. Hole position and alignment 

With a star piquet or peg, mark the ends of the proposed walls. Attach a string line to each peg or piquet, both on the top and bottom to keep the wall aligned. 

Start from one end of the wall and mark the ground at intervals, depending on your selected sleeper length. Make sure your bored piers are wholly contained with your own boundaries. 

3. Auger holes and pour concrete in 

Auger the holes as per your design guide or to the specifications of your engineer. Ensure posts are installed with a minimum lean back of 1:20 (50mm per 1.0m of height). 

There are two options for pouring the concrete: 

Option 1: Pour the concrete into the wholes one at a time, then set the post by lowering into the ground until level with the top string lines. 

Option 2: Set the post in its position with string lines and brace with temporary props (for example clamping a post between two timber planks and spanning plants over pier). Then pour concrete over all holes at the same time. 

4. Check your posts! 

Make sure all posts are aligned with string lines, use of a spirit level to make sure positioning is accurate. Confirm the height from the top of the concrete pier to to the top of the steel posts. The distance should be equal to an increment of 200 so your concrete sleepers will flush with the top of the post. 

If you need, install a concrete sleeper on each side of the post to guarantee correct positioning. Remember - if you are installing a fence, your fence brackets should be installed at this stage. 

5. Agi pipe, backfill with gravel and soil cap

Your concrete piers will need to cure for at least 3 days, or as specified by your engineer. 

Install your agi pipe at the base of the wall, ensure your geofabric is fully wrapped around the drainage gravel with 100mm lap top and bottom. Backfill with 300mm wide drainage gravel and wrap geofabric over and behind gravel. Then install you 150-300mm compacted soil cap over the geofabric and drainage gravel. 

Make sure surface finish directs stormwater flow away from the wall to a drainage pit. 

6. Enjoy your new wall!

Clean the site and landscape as per your plans. Your machine equipment and any heavy vehicles should not be used on the high side of the wall. Remember a minimum distance of 1 x Wall Height should be maintained. 

To make sure your is long lasting, no excavations should take place in front of the wall after completion. If you plan to build anything near the wall in the future, you will need to contact an engineer for advice. 

Building a retaining wall from concrete sleepers is an excellent way to manage soil erosion in your outdoor space. However, it’s important to keep in mind that proper drainage and foundation stability are crucial for the long-term performance of any retaining wall. In some cases, issues with the foundation can affect the integrity of your retaining wall, leading to costly repairs and potential structural problems. To ensure the stability of your foundation, it’s a good idea to consult with a foundation repair expert. They will be able to assess the condition of your foundation, recommend necessary repairs, and help you maintain a strong and stable base for your retaining wall, ensuring it stands the test of time.